The present invention relates to a new and improved construction of a blow-molding machine for the fabrication of hollow molded bodies or articles formed of thermoplastic materials.
Generally speaking, the blow-molding machine of the present development is of the type wherein the hollow blow molded bodies or articles are blow-molded in a hollow blow mold. This hollow blow mold is transported to-and-fro by means of a transport device containing a platform movable between a receiving station for receiving the hose-like thermoplastic material to be blow molded and a blow-molding station. The platform is equipped with means for receiving the hollow molded bodies or articles at the blow-molding station and for delivering the same to a delivery or outfeed station, such receiving means moving to-and-fro simultaneous with the to-and-fro movement of the hollow blow mold upon the platform between the blow-molding station and the delivery station.
It is well known in the blow-molding art that the transport devices of the blow-molding machine must move appreciable loads with considerable velocities. Between the individual work stations of the blow-molding machine a considerable mass must be accelerated and subsequently again decelerated i.e. braked prior to entry at the next successive work station, because the transport operation proceeds stepwise and cyclically. This large mass typically consists of the mass or weight of the devices which must be transported between the work stations, for instance a multi-part hollow blow mold along with the therewith operatively correlated mold closure facility of unit, and the inherent mass or weight of the transport device.
Frequently the transport path extends horizontally in space. This is afflicted with the drawback that a certain work stations the devices or facilities which are operative during the relevant working operation, for instance a blow molding head, must be intermittently shifted elevationally or laterally, in order to allow the transported device, for instance a closed mold unit, to move into such stations.
In order to at least partially eliminate such complications proposals have been made to design the transport paths such that they are inclined, in order that a transport step does not occur purely in the horizontal direction but also in the vertical direction, whereby a device can be introduced from below into a work station. However, in this case the otherwise advantageous vertical component of the travel path acts in a disadvantageous manner upon the transport operation and the equipment expenditure needed to accomplish the same, since it is necessary to now overcome the force of gravity through the use of an appreciable amount of energy and to terminate the transport step as free as possible from shock or impacts.
Consequently, the above-explained facts have resulted in massive and/or complicated constructions of blow-molding machines which are therefore not only extremely expensive but also prone to malfunction.
In order to reduce the load which must be transported attempts have been made to simplify the devices which have to be transported in order to save energy when moving these masses. Thus, there have been limited either the number of hollow molded bodies or articles which can be simultaneously fabricated, i.e. in a parallel production operation, or else a work operation which otherwise would have to be carried out during the progression of a transport step is eliminated and in lieu thereof there is provided an additional work station and related transport means for accomplishing the eliminated work step or operation. However, these measures prolong either the total production operation of the hollow blow molded bodies or else limit the production output of the machine, since fewer products can be simultaneously fabricated.
In U.S. Pat. No. 3,594,861, granted Jul. 27, 1971 there is disclosed a blow-molding apparatus wherein an extruder head deposits a parison into a mold which is supported by a linkage arrangement for movement into a position beneath the extruder head, through an aracuate path of travel, to a location remote therefrom. A second mold is likewise similarly mounted such that when the first mold moves out of its coacting relationship with the extruder head the second mold moves into a coacting position beneath the extruder head where parison can be deposited into such second mold. Apart from the possibility of cyclically operating the first and second swivelably mounted molds attention is not particularly paid as to the nature of and where the various stations are located and in what spatial relationship to one another or what operations, apart from the conventional mold actuation and filling steps, can be performed during the shifting of the mold from a position beneath the extruder to another remote location therefrom.